BINGHAMTON, N.Y. -- A faster response by emergency officials to the attack at an immigrant services center in Binghamton would have saved no lives, a county prosecutor said Sunday.

The shooting at the American Civic Association stopped shortly after the first 911 calls came in at 10:30 a.m., but police didn't enter the building until nearly 45 minutes later.

Survivors reported huddling for hours in a basement, not knowing whether they were still in danger after the gunman, 41-year-old Jiverly Wong, killed 13 people Friday.

Medical examiners who conducted autopsies on the victims reported that their injuries were so severe, they would not have survived, said Broome County District Attorney Gerald F. Mollen.

"Nobody could have been saved if the police walked in the door that first minute," he said.

The prosecutor's comments came at a news conference Sunday as officials prepared to release a list of names and home countries of the victims.

Four Chinese were among those killed, and a Chinese student was also shot in the arm and leg but survived, officials said. The other victims came from Haiti, Pakistan, the Philippines, Iraq, Brazil, Vietnam and the United States.

The first 911 calls came in at 10:30 a.m., police chief Joseph Zikuski said at a news conference. The callers spoke broken English, and it took dispatchers two minutes to sort out what was happening, he said.

The first patrol cars arrived at 10:33 a.m.

Officers were on the scene five minutes before a wounded receptionist called police to report a gunman in the building, Zikuski said. Police had earlier said it was that call that brought them to the immigration center.

A SWAT team entered the building 43 minutes after the first call to police.

When police got there, the gunfire had stopped, so they believed there was no "active gunman" in the center and decided to wait for the SWAT team to arrive, Zikuski said.

Zikuski said his officers would have gone into the building if shots had still been flying.

"If you arrive on the scene -- the first two to four guys -- and there's an active shooter, they enter," he said.

Pressed on why police didn't go into building, Zikuski said information they were getting from the receptionist was still uncertain enough to warrant caution.

"He was dead. We didn't know it," Zikuski said. "If there's a bunch of cops laying on the floor shot trying to rescue somebody else, it's not going to help anybody."

When reporters repeated the line of questioning, Mollen jumped in to defend the police chief.

"I don't think it's fair to ask Chief Zikuski to respond to hypotheticals," he said, adding that there would be a full review and report on the shooting, including the police response.

A former FBI agent who was also a member of a SWAT team said the response was appropriate.

"Lord, that seems like that was fast," said Harold Copus, who now runs a consulting company based in Atlanta. "When something like this happens, as you can imagine, it's mass confusion."

Wong was "an avid gunman" who had recently visited a firing range weekly, Zikuski said, but authorities still don't know his motive.

Authorities don't know whether he had a particular target, and Zikuski said the choice of targets may have even been random.

Officials have said Wong was apparently upset about losing his job at a vacuum plant and about people picking on him for his limited English.